Locking circuit



May 19,1942. I G J,MAK. 2,283,381

LOCKING CIRCUIT Filed Aug. 24, 1940 INVENTOR. 610965 J: 070/ Patented Ma 19, 1942 LOCKING CIRCUIT George J. Maki, Elmhurst, nr, assignor to ma Corporation or America, a corporation oi Delaware Application August 24, 1940, Serial No.-354,033

4 Claims.

Thi invention relates to locking circuits and regenerating devices in both multiplex and simplex circuits.

The invention will be described in connection with a multiplex transmission circuit, but its application to multiplex receiving circuits or to simplex transmitting and receiving circuits will be apparent therefrom.

It is an object of my invention to provide a locking circuit that is simple and of lower cost than those heretofore in use. 1

Another object of the invention is to provide a locking circuit, operating without inertia, that requires only a single tube. a

Another object is to provide a locking circuit consisting of a single gas tube of the two-electrode type.

Other objects of the invention will appear in the following description, reference being had to the drawing in which the single figure is 8. diagrammatic illustration of the improved locking circuit used for keying a transmitter in a multiplex telegraph circuit.

Referring to the drawing, reference character I diagrammatically illustrates a source of direct current potential across the terminals of which is placed a potentiometer resistance 2. A twoelectrode gas tube 3, which by way of example may be a neon tube, is connected across points B and D of the potentiometer through a resistance 4. The positive high potential point A is connected to the marking contacts M of contactors I, II, III, such as are used in tape transmitters in multiplex transmission, there being three channels assumed in this particular illustration. The spacing contacts S are connected to the point C, which i negative in respect to the point A.

The movable contacts 5 of transmitter I are connected to contact 6 in the distributor I and the movable contacts 8 and 9 of the transmitters II and III are connected to contacts I and II, respectively, in this distributor. The movable contact arm I2, which is rotated continuously as in the usual multiplex transmitter, is connected to the contact 13.

The changing potential in resistance 4 is employed to operate tone keyer I3 and connections maybe made for sending out tone frequency either for the marks or for the spaces, as desired. By way of example, I have shown the tone keyer l3 with 'the positive terminal of resistance 4 connected to unblock the push-pull tubes l4, l when a mark signal is transmitted, the negative terminal of the resistance 4 being connected to the cathodes of tubes l4, l5 through a suitbe connected to a transmitter 01 any desired type. Since my invention,.per se, does not relate to the transmitter, this has not been illustrated.

The action of my improved locking circuit takes advantage of the difference between the striking and extinguishing voltages of a gasfilled tube such as a neon tube, for example. Various characteristic values may be adopted, but merely by way of example I will say that I have obtained good results by using volts at the source I, with a 250,000 ohm resistor 4 in series with the neon tube. The contacts B and C may then be adjusted so that the voltage across AB is 16.5 volts and that across AC is 35 volts.

The operation of my invention will now be described.

Let it be supposed that-channel No. 1 is sending a mark. Contactor I'will thus be in engagement with marking contact M and the resistance between points A and B will be momentarily short-circuited. This will raise the voltage applied to the neon tube 3 to the striking point and it will conduct current. The potential drop in resistance 4 will then apply sufficient positive voltage to the input of the keying tubes 14, I5 to overcome the blocking negative bias l6 and the tone frequency of generator l8 will be applied to transformer I1 and sent to the transmitter (not illustrated).

-When the distributor arm l2 leaves contact 6, neon tube 3 i not extinguished even though the short-circuit between points A and B has been removed. This is because the extinguishing voltage of the tube is considerably less than the striking voltage. Consequently, the tone current continues to be sent to the transmitter in the same way as disclosed in the more complicated locking circuit of Callahan Patent 2,086,351, June 6, 1937.

The marking condition established by channel No. 1 will continue until the distributor arm l2 engages a contact on the distributor I that has been connected to a spacing contact on the tape transmitter. Therefore, if the succeeding con- 7 tact Ill has been connected to the marking contact by movable contact 8, no change takes place in keyer l3, but if keying lever 8 is moved to the spacing contact in channel No. 2, when contact arm l2 engagesv contact I 0, the resistance between points B and C will be short-circuited and this will reduce the voltage applied to the neon tube 3 to such a point that the tube is extinguished. In this situation, negative bias I6 blocks the push-pull keying tubes and tone frequency from generator 18 cannot pass'to the transmitter. A spacing signal is therefore transmitted. This spacing signal will continue until the distributor arm I2 engages some contact that is set for a marking signal, which will momentarily short-circuit the resistance between the points A and B again and cause the neon tube to strike and send a marking signal.

It will be seen that my invention very materially simplifies the usual locking circuit, for example, the one described in the Callahan patent hereinbefore mentioned, in that only one two-element tube is required. This one tube performs the functions of locking circuits heretofore used.

Having described my invention, what I claim is:

1. In signalling circuits, a gas tube having an extinguishing voltage materially lower than its striking voltage, a voltage source consisting of a potentiometer resistance, a transmitter key having a mark contact connected to a high potential point in said resistance and a space contact connected to a lower potential point therein, said transmitter key having a switch tongue connecteclto an intermediate potential point in said resistance, said gas tube having one electrode connected to a point in said resistance that is negative in respect to said lower potential point, and a resistance connected between the other electrode of said tube and said intermediate potential point, said potential points being selected on the first-mentioned resistance so that said tube conducts when the tongue is on the mark contact and extinguishes when it is on the space contact.

2. In signalling circuits, a gas tube having an extinguishing voltage materially lower than its striking voltage, a voltage source consisting of a potentiometer resistance, a transmitter key having a mark contact connected to a high potential point in said resistance and a space contact connected to a lower potential point therein, said transmitter key having a switch tongue connected to an intermediate potential point in said resistance, said gas tube having one electrode connected to a point in said resistance that is negative in respect to said lower potential point,

a resistance connected between the'other elec-,

, mentioned resistance.

- 3. In signaling circuits, a gas tube having an extinguishing voltage materially lower than its striking voltage, a voltage source, a transmitter key having one signal contact connected to a high potential point in said source and a second signal contact connected to a lower potential point therein, said transmitter key having a switch tongue connected to an intermediate potential point in said source, said gas tube having one electrode connected to a point in said source that v is negative in respect to said lower potential point, and the other electrode of said tube being connected to said intermediate potential point, said potential points being selected on the voltage source so that tube conducts when the tongue is on the first contact, extinguishes when it is on the second contact and maintains its state as to conductivity when it is connected to neither of said contacts.

4. In signaling circuits, a gas tube having an extinguishing voltage materially lower than its striking voltage, a voltage source, a transmitter key having one signal contact connected to a high potential point in said source and a second signal contact connected to a lower potential point therein, said transmitter key having a switch tongue connected to an intermediate potential point in said source, said gas tube having one electrode connected to a point in said source that is negative in respect to said lower potential point, a signaling device connected between the other electrode of said tube and said intermediate potential point, said potential points being selected on the voltage source so that said tube conducts when the tongue is on the first contact, extinguishes when it is on the second contact'and maintain its state as to conductivity when it is connected to neither of said contacts.

GEORGE J. MAKI. 

